I have a mesh with three Deco X90s (one of which is my main) and four Deco M5s. Maybe a bit overkill, but this setup has worked fine for several years.

A couple of days ago, I upgraded firmware on the X90s, and since then my wifi speed is broken. I have a 1000/1000 Mbps connection (from which I usually can get 300-500 Mbps at least). Now I get 5-20 Mbps download and often < 1Mbps upload. It's a radical difference, and clearly happened at the time of the X90 firmware upgrade.

The drop in speed isn't completely consistent -- it does happen that I get a high speed when testing (although not more than 1 out of 5 tries). Also, when using a cable, I consistently get the old performance, so it's not related to my broadband connection.

Please help.